One common treatment for male erectile dysfunction is the implantation of a penile prosthesis. An exemplary inflatable penile prosthesis 10 is shown in FIG. 1. Penile prostheses typically include a pair of inflatable cylinders 12, which are fluidly connected to a reservoir 14 via a pump and valve assembly 16 through tubing 18. The two cylinders 12 are normally implanted into the corpus cavernosae of the patient and the reservoir 14 is typically implanted into the patient's abdomen. The pump assembly 16 is implanted in the scrotum. A detailed description of the exemplary penile prosthesis 10 is provided in U.S. Publication No. 2006/0135845, which is hereby incorporated by reference herein.
During use, the patient actuates the pump 16 and fluid is transferred from the reservoir 14 to the pump 16 through tubing 20. The fluid travels through the pump 16 and into the cylinders 12 through tubing 18. This results in the inflation of the cylinders 12 and thereby produces the desired penis rigidity for a normal erection. Then, when the patient desires to deflate the cylinders 12, a valve assembly within the pump 16 is actuated in a manner such that the fluid in the cylinders 12 is released back into the reservoir 14. This deflation then returns the penis to a flaccid state.
The pump and valve assembly 16 includes fluid pathways allowing the flow of fluid to and from the reservoir 14, as well as to and from the cylinders 12. In some designs this fluid flow is controlled by one or more poppet valves positioned in the fluid pathways within the housing of the pump and valve assembly 16.
A compressible pump bulb 22 is typically attached to the housing 24 of the pump assembly 16 and is in fluid communication with the various fluid pathways. In order to inflate the cylinders 12, the compressible pump bulb 22 is actuated by the patient, thereby urging fluid in the bulb 22 past the poppet valves into the cylinders 12. In order to deflate the cylinders 12, the valve housing 24 is grasped and squeezed, such as at button 26, through the patient's tissue, causing the various poppet valves to unseat and allow fluid to flow back to the reservoir 14 through a ball check valve (i.e., bypass valve) contained in the housing 24.
FIG. 2 is simplified illustration of an exemplary bypass valve 30 during cylinder inflation or a steady state condition. The bypass valve 30 includes a poppet 31 in the form of a spherical valve member 32 within a bypass cavity 34. The valve member 32 is biased against a valve seat 36 of an input port 38 of the cavity 34 by a spring 40. The coils of the spring 40 are not shown in the figures in order to simplify the illustrations.
FIG. 3 is a simplified illustration of the bypass valve 30 during cylinder deflation. During deflation of the cylinders 12, the operator releases the seal formed by various poppet valves within the housing 24 to direct a flow of fluid, represented by arrows 42, from the cylinders 12 through the input port 38 of the bypass cavity 34. The pressure of the flow of fluid overcomes the bias force supplied by the spring 40 and displaces the valve member 32 from the valve seat 36. The flow of fluid 42 travels through the bypass cavity 34, through an output port 44 and back to the reservoir 14, as mentioned above.
As the flow of fluid is continuously modulated by the throttling of the valve 30, the ball 32 moves rapidly (vibrates) toward and away from the valve seat 36, as indicated by arrow 46. This vibration induces an audible sound outside of the pump 16. As the velocity of the flow decreases in response to decreasing pressure within the cylinders 12, the frequency of the sound increases, eventually sounding like a high pitched scream (approximately 3000 Hz) toward the end of the deflation operation.